Gas, in particular steam, treatment of foods and other products is a widespread practice and the growing government and consumer awareness of microbial contamination of foods means the use of steam and other gas treatments will greatly increase. Consumer demand for high quality and a wide variety of foods will also increase the use of such treatments. Better gas treatment systems are needed particularly to provide better treatment, to treat less resilient foods, and to increase profitability. One example of gas treatment is the steam cooking of vegetables. It is conservatively estimated that the current market for the subject gas treatment apparatus is 1,000 units in the U.S. and 10,000 units worldwide for food applications alone. The market for non-food applications is expected to be considerable also.
From a food safety perspective, microbial contamination accounts for more than 90 percent of unconfirmed food-borne illnesses. The Centers for Disease Control (CDC, 1999) estimates 76 million cases of food-borne illnesses, 325,000 of which result in hospitalization and 5,000 in deaths annually because of microbial contamination. The annual cost of these illnesses is approximately $8.4 billion. The portion of that cost which can be attributed to improper commercial processing is not clear but empirical evidence suggests that it is an important contributor.
The invention provides a means of containing the treatment gas in a treatment chamber and also transferring the product into the treatment chamber and then out of the treatment chamber while minimizing the loss of treatment gas and preventing unwanted gases from entering the treatment chamber. Elsewhere mechanical air locks have been used to exclude unwanted transfer of gasses. However, opening of the airlocks allows significant volumes of the treatment gas to escaped and/or significant amounts of gases from external sources to enter the treatment chamber. Using mechanical means alone to exclude transfer of gases is often capital intensive, and the efficacy is less than desirable.
Air or other unwanted gases carried into a gas treatment chamber dilutes the treatment gas, and may otherwise reduce its effectiveness. The introduction of unwanted gases also increases the total mass of the gas and this extra mass may create handling problem to prevent pollution. The treatment gas may also be carried out of the treatment chamber with the product, and, while a certain amount may be beneficial, large amounts are generally problematic because of the cost of replacing the treatment gas and the safety/pollution problems it may pose. Such transfers of air and/or treatment gas are objectionable because they increase the cost or reduce the effectiveness of the treatment. Hence, there is a need for a gas treatment chamber that reduces the escape of treatment gas from the chamber and reduces the introduction of air or other unwanted gases into the treatment gas.
U.S. Pat. No. 887,628 to Hall describes a steaming apparatus having a conveyor belt. However, water or other dense medium is not used to retain the steam in the casing. Similarly, U.S. Pat. No. 6,153,240 to Tottenham et al. describes an apparatus and method for food surface microbial intervention and pasteurization. However, the described method does not include passing the treated object through an intermediate fluid before treatment.
U.S. Pat. No. 3,880,068 to Goodale describes an apparatus for washing and blanching of vegetables, the blanching chamber having a water seal. Other food treatment apparatus are described in U.S. Pat. Nos. 6,263,785 and 4,942,810 to Zittel; U.S. Pat. No. 4,962,777 to Bell; U.S. Pat. Nos. 4,604,948 and 4,547,383 to Goldhahn; and U.S. Pat. No. 4,092,911 to Goodale.
However, the prior art fails to describe an apparatus for treating objects with a treatment gas, the apparatus having a treatment chamber, a chamber input, and a chamber output, the chamber input and chamber output including media through which the objects pass, the media preventing escape of the treatment gas from the treatment chamber and ingress of external gases into the treatment chamber.